The present invention relates to spectroscopy, and more particularly to the use of infrared absorption spectroscopy in identification of an unknown gas.
Infrared absorption spectroscopy involves generating an infrared spectrum for a material such as a gas or vapor. A material's infrared spectrum is a measure of the tendency of the material to absorb infrared energy having wavelengths that vary across a predetermined band of infrared wavelengths. For example, many applications use the mid-infrared spectral band, which includes wavelengths from 2.5 micrometers to approximately 14 micrometers. The material's infrared spectrum is generated by measuring the degree of absorption for each wavelength in the spectrum, and plotting absorption versus wavelength.
Different chemical compounds produce vastly differing characteristic spectral profiles or "signatures" over the mid-infrared spectral band, by which they can be readily recognized. Thus, to identify an unknown gas, the infrared spectrum of the unknown gas is visually or mathematically compared with the infrared spectra of a number of reference gases. By comparing the unknown spectrum with a library of reference compounds, the most likely match to the unknown gas can be determined. If the shape of the infrared spectrum of the unknown gas matches that of the infrared spectrum of a reference gas within a defined tolerance, there is a high probability that the two gases are the same.